Air curtain



Oct. 12, 1965 F. A. KRAMER, JR 3,211,077

AIR CURTAIN 16/5 Si 63 l l 5) 7.3/

Filed Nov. 22, 1961 2 Sheets-Sheet 1 Uri* fm Huw f// V===l=` c' yI |lA Oct. l2, 1965 F. A. KRAMER, JR

AIR CURTAIN 2 Sheets-Sheet 2 Filed Nov. 22, 1961 /fw/E /To re:

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ATTO @NE YS United States Patent O 3,211,077 AIR CURTAIN Frederick A. Kramer, Jr., 12040 Conway Road, St. Louis 31, M0. Filed Nov. 22, 1961, Ser. No. 154,175 6 Claims. (Cl. 98--36) This invention relates to an air curtain for restricting the transfer of heat through an open doorway or other opening in the wall of a building. In general, this air curtain is assembled as a self-contained unit, including a housing and a blower fan supported within the housing. A vent through a side of the housing supplies intake air to the .blower or tan. A series of bailes or vanes are positioned adjacent the air discharge side of the fan to direct the blown air through an outlet or outlets in the bottom wall of the housing in a direction that is bot-h downward and somewhat inclined toward the opening above which the housing is mounted. The discharge air baffles are especially arranged and positioned to regulate the shape of the discharge air to a screen of air of substantially uniform velocity over its entire width.

The broad eld of air screens or air curtains is certainly not new, but the approach to the problems involved in the art is new as embodied in this invention. As is known, the purposes of an air curtain or air screen include the reduction of heat transfer through a building opening, the reduction of drafts through the opening, and the repulsion of insects which attempt to enter the building through the opening. The development of the art has reached a point which is popularly believed to best accomplish these purposes. The conventional air curtain includes a fan or fans :for mounting above an opening in a building and capable of directing a Very high speed stream of air across the opening. The fan is usually provided with an infinitely variable speed control. Below the fan, the lioor has a grating for receiving the discharge air and there are ducts which convey the air through the iioor and walls of the building back to the fan inlet. The theory behind these conventional air curtains is that the duct and grating draw the air downwardly to produce a more highly unyielding air curtain.

The concepts of this invention do not begin with these highly complicated systems which require considerable modilications to a building and are difiicult to install. To

the contrary, this invention is based upon the principle that if a room is designed so there are no cross-drafts between opposing openings, the air pressure within the room will quickly equalize to the air pressure outside the room. Then, under static wind conditions outside an opening, the pressure inside the opening will balance the pressure outside the opening, and air will neither enter nor leave the room through the opening. Furthermore, this inventor recognizes that a curtain of air blown across a doorway or other building opening, the velocity of which is limited to what people passing through the opening will allow to be blown upon them, is readily deliectable. Mild outside wind gusts directed toward the opening will bend the lower end of the air curtain inwardly toward the room. Under these conditions, if the air curtain is provided with a grate in the oor beneath the air stream, the curtain will be bent away from the grate and will not enter the grate at all.

vHowever, a large portion of this outside air (cold air in winter) will enter the grate and be carried by the ducts to the Afan inlet. Then the curtain will blow cold outside air across the opening because, even if heaters are provided for air entering the fan, they cannot work quickly enough to warm the rapidly moving captured outside air. Hence, under static wind conditions, the air curtain does not actually function to repel the outside air because the outside air is keptv out by the equalized pressure inside the 3,211,077 Patented Oct. 12, 1965 building. Under these static conditions, a grate is not necessary. As soon as wind gusts blow, the air stream is bent inwardly well beyond the practical limits of a grate. Then, the grate does 4not provide a return for the air curtain, but draws much of the outside air into the blower.

In the present air curtain system, no grate is used. The entire operating unit is self-contained within the housing mounted above the building opening. The air stream strikes the floor beneath the housing. When wind gusts do occur, they bend the air curtain inwardly but are kept close to the lioor by the air curtain, the velocity of which is lowest at the lower end and Ihigher toward the upper end. This outside air near the floor is churned into turbulence by the air curtain which mixes inside air with the outside air to greatly reduce drafts.

The primary object of the invention is to provide an air curtain which utilizes the principle of equalized air pressure on opposite sides of a building opening and prof vides a screen across the opening to restrict heat transfer through the opening and to repel insects, dust, and the like.

Another object of the invention is to provide a compact, self-contained unit for creating an air curtain across a doorway to a building.

Still another object of the invention is to provide a self-contained unit that can be quickly mounted above an opening to a building and which contains all of the parts necessary to generate an air curtain across the opening.

Yet another object of the invention is to provide a self-contained air curtain including a housing with means to direct infra-red heat from the housing across a buildin opening to heat the surface below the housing.

Still another object of the invention is to provide an air curtain including an attractive housing for. containing the operating parts of the air curtain, which housing has' means for illuminating the area below the housingv and means for permitting illuminated displays on the side o the housing. `v

Another object of the invention is to provide a self- `contained unit for discharging a curtain of air Afrom above'` the doorway across the doorway, including a housing with a fan supported within the housing, and means including vanes within the housing for directing the dischargel air over a wide area at substantially uniform air speeds across the width of the curtain.

Another object of the invention is to provide a selfcontained air curtain unit that includes a housing and means within the housing for directing a'stream ofair below the housing, the housing being designed to permit mounting alongside similar housings to accommodate door--v ways or other building openings of various widths.

Other objects and advantages will be apparent to those` skilled in the art.

In the drawing:

FIGURE 1 is a plan view on a reduced scale of the' air curtain housing;

FIGURE 2 is a side elevation view of the housing ofv FIGURE l;

FIGURE 3 is a front elevation view of the housing of FIGURES l and 2 as viewed from the right side of FIG- v URE 2;

FIGURE 4 is a bottom view of the air curtain assembly;

FIGURE 5 is Ia side elevation view in section taken along th-e line 5 5 of FIGURE l;

FIGURE 6 is a plan view in section taken along the line 6-6 of FIGURE 2;

FIGURE 7 is a view in section taken along the line 7-7 lof FIGURE 5;

FIGURE 8 is `a view in section taken along the line I 8 8 of FIGURE 5;

FIGURE 9 is a side elevation view partly in section,

showing the air curtain unit installed on the inner side of a building wall above a doorway and showing one means for supplying makeup air to the fan inlet;

FIGURE is a schematic plan View of a room with two of the air curtain units installed over a doorway and with a different fan arrangement for supplying makeup a1r to the air curtain units; and

FIGURE 1'1 is a fragmentary front elevation view of two sligh-tly modiiied air curtain units, particularly illustrating a means for fastening the units together in sideby-side relationship.

Referring to FIGURE 1 of the drawing, the arr cur- .tain apparatus is entirely contained within a housing 10. This housing has a front wall 11, side walls 12, a rear wall 13, and a top wall 14. The lower edge of the front wall stops short of the bottom of the housing. These walls 11, 12, 13 `and 14 are made of sheet metal joined together at the adjacent edges by conventional methods. The forward edge of the top wall is trimmed with a heavy extruded aluminum strip 15 which projects forward of the front wall 11. Similar extruded aluminum strips 16 are fastened to the forward end-s of the side panels 12, but these strips 16 extend downward and rearwardly from the upper strip 15. The lower edges of the side panels 12 also have heavy `extruded aluminum trim strips 17.

There is a similar aluminum strip 18 connected between the lower edges at the forward ends of the strips 17 and a strip connecting the lower rear corners of the side walls 12, The aluminum strip 18 is removable and is fastened by screws 20 to ya sheet metal strip 21, .the strip 21 in turn being welded to the side walls 12 of the housing. The strip 19 is welded to the side walls 12 and the rear wall 13 and has threaded halves 22.

A yhorizontal sheet metal partition 26 extends from the rear wall 13 toward the front wall 11. This partition 26 is welded to the side walls 12 and the rear wall 13 of the housing. The forward end 27 lof the horizontal partition 26 has a fairly sharp ybut smooth bend that joins the partition to a downwardly and rearwardly extending wall 28. The partition 26 supports a centrifugal fan 29 which has a central air inlet 30 communicating with a converging passage 31 in the upper wall 14 of the housing. The fan has radial blades 32 past which air is discharged from the fan. The motor l33 which drives the fan is positioned below the partition 26 and is bolted thereto.

A curved wall or scroll 36 is welded between the upper wall 14 and the horizontal partit-ion 26. This curved wall 36 is a well-known means for providing `a space 37 of gradually increasing size. The air discharged from the fan 'is collected within the space 37 and directed toward the space opposite the forward edge 38 of the curved wall 36. However, because of the centrifugal effect-s of the discharged air, the speed and pressure of the air is greatest near the wall 36, and, therefore, as the air approaches the front wall 11 of the housing, the speed of the air across the width of the housing is far from uniform. To redistribute this discharged air, the housing is provided with a series of bailles or vanes 39, 40, 41 and `42 and With a diffuser 43. The baille 39 has a smooth bend 44 positioned next to the radial blades 33 of the fan. The balle 40 has similar bend 40a and the baille 41 has a bend 41a. The baille 42 is straight. All of these baffles are made from sheet metal fastened to the top wall 14 and to the horizontal partition 26.

The diffuser 43 extends across the width of the housingand between the top wall 14 and the horizontal partition 26. This diffuser comprises a pair of superposed quarter inch mesh wire screens dis-posed diagonally to one another. The diffuser 43 'impedes the ilow of air past it, allowing the lair to redistribute itself before passing through the screen. As a result of the batlles 39, 40, 41 and 42, and of the diffuser 43, the speed of the air after it has passed the diiluser 43 is practically uniform over the entire width of the housing 10.

There are additional bailles forward of the diffuser 43.

As already mentioned, a wall 28 extends downwardly and rearwardly from the horizontal partition 26. A sirmlar downwardly and rearwardly extending wall 45 1s positioned forward of the wall 28 and has an upper end 46 that is curved and then joined to the top wall 14 of the housing. The walls 28 and 45 are `spaced apart by substantially the same `amount as the spacing between the top wall 14 and the horizontal partition 26.

Two vanes 47 and 48 are positioned between the walls 28 and 45. These vanes 47 and 48 also extend downwardly and rearwardly. The vanes 47 and 48 also have curved upper ends 49 and 50, respectively. All of .the walls 28, 45, 47 and 48 extend across the entire width of the housing and are welded lto the side walls. They divide the air stream -into three passages 51, 52 and 53 of equal width and depth and discharge the air downwardly and rearwardly of the housing 10, at an angle of about 20 to the vertical. To Akeep the depth of the passages uniform, a plate 54 is fastened to each of the walls or vanes 47 and 48. Those plates 54 are bent to the same degree of curvature as the bend 27 in the wall 28. Because these three Aair streams are slightly separated as they emerge from the housing, the center arr stream tends to entrain air from the outer air streams as the air moves downwardly, producing a slightly converging eifect upon the total air stream. This slightly converging efect tends to increase the vel-ocity of the air as it approaches the iloor, thereby ysomewhat counteracting the overall decrease in velocity of the air curtain.

Turning to further structural features of the housing 10, there is a iluorescent lamp 56 horizontally mounted between the side walls of the housing. A glass, plastic or other transparent panel 57 is fastened to the forward edges of the aluminum strips 16 a-t the lower front side of the housing. The front wall 11 of the housing terminates short of the lower wall and the panel 57 is thus illuminated by the lamps 56. Hence, a sign or advertising may be painted or ailixed to the panel 57 to be illuminated by the lamp 56.

Slightly rearward of center there are two additional fluorescent lamps 58 mounted horizontally between the side walls 12, slightly above the bottom of the housing. These lamps 58 provide illumination for the entrance below the air curtain. A plastic line 59 is supported between the sidewalls 12 below the lamps 58.

Two infra-red heaters 60 and 61 are supported by the side walls 12 Within the housing. These heaters are of conventional construction of quartz tubing surrounding a heating element. One of these heaters 60 is positioned forward of the iluorescent lamps 58 and the other heater 61 is positioned rearwardly of the fluorescent lamps 58. There is a curved aluminum rellector 62 surrounding the upper side of the heater 60. This reflector directs the heat from the lamp 60 in the general direction of the air curtain discharged from the passages 51, 52 and 53. A similar curved aluminum reflector 63 surrounds the upper side of the heater 61 and directs its heat in the direction of the lloor below the doorway and the ground just outside the doorway.

The housing 10 is easily installed above an opening to` a building. For example, it may be installed against the inner side of a wall 65 above a doorway 66 so that the doors can be left open. First an angle iron member 67 is fastened by screws 68 to the wall 60. Next the lower rearward'edge of the housing is set upon the angle iron member 67 and is secured by screws 69, that extends intol the holes 22 of the stop 19. Then the forward end of the housing is suspended from the room ceiling by a tension rod 70. This tension rod 70 has a head 71 that is'y freely rotatable within a bracket 72, the bracket being attached to the ceiling structure. The top wall v14 of the housing is threaded and the lower end l'Z3 of the rod 70 is threaded so that the height of the fonward end of the housing 10 can be adjusted by rotating the rod 7th. When the housing is level, a locknut 74 .its tightenpvfl: @W11 against the top 14 of the housing. Finally, the lower front aluminum plate 18 is removed and a grille 75 of aluminum of egg crate is placed upon the ledge 19 at the rearward end thereof and is held in place at its forward end by replacing the aluminum plate 18.

With the foregoing installation, there may be times when the fan 29 is supplied with suicient air from recirculation of the air curtain or from the small amount of air that enters the building through the doorway 66. At other times it may be desirable to provide an external supply of air. The external supply of air has the additional advantage of maintaining pressure within the room equal to outside pressure. With an external air supply, changing outside pressure conditions can be more rapidly duplicated inside the room.

As shown in FIGURE 9, a convenient way to supply external air to the fan inlet is to provide an intake fan unit 78 above the air curtain unit and through the same wall. The intake fan unit may be supported within a housing 79 including a lter 80 and a conventional fan 81.

The external air supply fan need not be located next to the air curtain housing 10. As shown in FIGURE 10, a fan 82 is positioned on a wall opposite the air curtain. Such a fan will work equally as well as the fan arrangement illustrated in FIGURE 9 so long as it has a capacity that will maintain the air pressure within the building or room equal to the air pressure outside the room. If the pressure within the room drops below the outside pressure, there will be a ow of air through the buildling opening until the pressure is equalized unless the additional air pressure is supplied by the fan. It can also be seen in FIGURE that the regular building doors 83, when opened, provide convenient side walls to conne the air curtain.

FIGURE l0 also illustrates two housing units 10 mounted alongside one another representing a slightly modied form of the invention. One of the features of the invention is the provision of means for readily attaching two or more housings together. Such attachment means are shown in FIGURE 11. Each side of a housing 10 has a pair of anges 85 extending upwardly. Opposing ones of these anges are fastened together by a bolt 86 and held apart by a spacer 87. At the lower end of the housing, the side walls 12 have holes 88 through them. There is ready access to these holes upon removal of the grille 75. After the spacers 89 are put in place, these lower side walls are fastened together by bolts 90. The housings are each about two feet Wide (and about one foot high and three and one-half feet deep) and any number of the housing units may be fastened together to accommodate various door widths.

Various changes and modications may be made within the process of this invention as will be readily apparent to those skilled in the art. Such changes and modifications are within the scope and teaching of this invention as deiined by the claims appended hereto.

What is claimed is:

1. An air curtain device comprising a housing having top, bottom, and lateral side walls, a blower supported within the housing, an air inlet through a side of the housing to supply air to the blower, an air outlet through the bottom side of the housing for permitting air discharged from the blower to pass from the housing, the air outlet having vanes for regulating the direction of ow of air from the housing, air passage means for directing air from the blower to the air outlet, means for mounting the housing above a door opening to a room, and means adjacent the outdoor side of the air outlet and mounted in position to direct heat rays directly toward the air flowing from the housing to heat both the floor and air.

2. An air curtain device comprising a housing having top, bottom, and lateral side walls, a blower supported within the housing, an air inlet through a wall of the housing to supply air to the blower, an air outlet through the bottom wall of the housing for permitting air discharged from the blower to pass from the housing, the air outlet having vanes for regulating the direction of flow of air from the housing, air passage means for directing air from the blower to the air outlet, means for mounting the housing above a door opening to a room, and means adjacent the outdoor side of the air outlet for radiating infra-red heat rays downward from the housing toward a oor of a room and toward the air ilowing from the housing to heat both the oor and air.

3. The combination of claim 2 wherein the housing has means for directing illuminating light rays downwardly from the housing.

4. The combination of claim 2 wherein the front wall of the housing has illuminated panel means for accenting advertising insignia and the like inscribed upon the panel means.

5. The combination of claim 2 wherein the housing has planar parallel side walls with the air outlet extending substantially the full width of the housing between the side walls, and means to fasten adjacent side walls of two of the said air curtains together to provide a composite wide air curtain, a plurality of identical air curtains alongside one another.

6. An air curtain comprising a housing mounted above a building opening, a blower fan contained within the housing, an air intake to the fan, passage means within the housing to convey air from the air intake to the fan, air discharge means through the lower wall of the housing, second passage means within the housing to convey air from the fan to the air discharge means, an infrared lamp means adjacent the outdoor side of the air discharging means in the lower part of the housing for directing heat rays to heat the discharge air and the surface below the housing, and means comprising vanes in the second air passage means, the vanes having sides inclined downwardly and toward the building opening for directing air from the air discharge means past the infra-red heat rays and toward'the said surface below the housing.

References Cited by the Examiner UNITED STATES PATENTS 1,064,140 6/ 13 Gillespie 98--36 X 2,073,744 3/37 Henney 98-36 X 2,150,252 3/39 Shure 98-36 X 3,023,688 3/62 Kramer 98-36 3,059,563 10/62 Larson 98-36 3,086,441 4/ 63 London 98--36 FOREIGN PATENTS 872,601 7/ 61 Great Britain.

WILLIAM F. ODEA, Acting Primary Examiner.

NORMAN YUDKOFF, ROBERT A. OLEARY,

Examiners. 

1. AN AIR CURTAIN DEVICE COMPRISING A HOUSING HAVING TOP, BOTTOM, AND LATERAL SIDE WALLS, A BLOWER SUPPORTED WITHIN THE HOUSING, AN AIR INLET THROUGH A SIDE OF THE HOUSING TO SUPPLY AIR TO THE BLOWER, AN AIR OUTLET THROUGH THE BOTTOM SIDE OF THE HOSUING FOR PERMITTING AIR DISCHARGED FROM THE BLOWER TO PASS FROM THE HOUSING, THE AIR OUTLET HAVING VANES FOR REGULATING THE DIRECTION OF FLOW OF AIR FROM THE HOUSING, AIR PASSAGE MEANS FOR DIRECTING AIR FROM THE BLOWER TO THE AIR OUTLET, MEANS FOR MOUNTING THE HOUSING ABOVE A DOOR OPENING TO A ROOM, AND MEANS ADJACENT THE OUTDOOR SIDE OF THE AIR OUTLET AND MOUNTED IN POSITION TO DIRECT HEAT RAYS DIRECTLY TOWARD THE AIR FLOWING FROM THE HOUSING TO HEAT BOTH THE FLOOR AND AIR. 